Herpes simplex virus, when inactivated by ultraviolet light, undergoes profound changes besides inactivation of its infectious capability. We have recently discovered that UV-inactivated virus has a strong therapeutic action against acute herpes simplex infections of the cornea. Dendritic ulcers rapidly disappear, inflammation clears overnight and regrowth of denuded epithelium is rapid. This project is an effort to develop optimum conditions for production of the responsible agent(s) to isolate and identify it and to determine its mechanism of action in experimental corneal infections.